Cable-type coring apparatus for retrieving underground specimens

ABSTRACT

A cable-type coring apparatus comprises a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing, and means for retrieving the head with a cut core therein. Water under pressure forces the coring head and retrieval means downwardly until the head locks in coring position in the tubing with a latch action. An upward pull on the cable unlatches the head and also vents the water under pressure so that it no longer forces the assembly downward, whereupon continued pulling on the cable retrieves the coring head and cut core.

United States Patent [151 3,667,558

Lambot 1451 June 6, 1972 54] CABLE-TYPE CORING APPARATUS 3,420,322 1; 1969 Mark 2.1.1 132246 3,333,647 8 1967 Karich et ..1 24

FOR RETRIEVING UNDERGROUND 2,148,373 2 1939 Garfield ..175/247 SPECIMENS 3,103,981 9 1963 Harper ..l75/246 x Z6 E 62 z 61 43 Primary Examiner-David H. Brown Attorney-Young & Thompson [57] ABSTRACT A cable-type coring apparatus comprises a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing, and means for retrieving the head with a cut core therein. Water under pressure forces the coring head and retrieval means downwardly until the head locks in coring position in the tubing with a latch action. An upward pull on the cable unlatches the head and also vents the water under pressure so that it no longer forces the assembly downward, whereupon continued pulling on the cable retrieves the coring head and cut core.

2 Claims, 16 Drawing Figures PATENTEDJUH 6 i972 SHEET U, BF 6 max/flak CABLE-TYPE CORING APPARATUS FOR RETRIEVING UNDERGROUND SPECIIVIENS The present invention relates to coring apparatus for cutting and retrieving specimens of earth or rock from underground so that the cut and retrieved cores can be examined. The apparatus is more particularly of the type comprising a string of coaxial tubes that turn together about their vertical axis and carry an annular coring bit at their lower end. The core thus cut and formed extends progressively into a coring head that has an extractor and that can be withdrawn upwardly within the string of tubing, by pulling on a cable.

In known coring apparatus of this type, fluid under pressure presses a coring head downwardly and acts on the coupling means for this head and on an annular packing ring which serves as a piston. The annular packing ring is mounted on the coupling means and is disposed between the end of an uncoupling tube and the coring head. As a result of fluid pressure and the axial translation of the head downwardly, the packing ring acts against the end of the uncoupling tube so as to come to rest in its plane and so as to be in fluid-tight contact with the corresponding external tube. Upon reverse movement of the coring head when pulling on the cable, the uncoupling tube slides axially relative to the rest of the coring head. As a result, the packing ring is distorted relative to the uncoupling tube and is displaced by the fluid under pressure which tends to escape along the side of the coring head.

Also in known coring apparatus, the fluid under pressure which displaces the retrieval means downwardly also acts on the body of the retrieval means and on another packing ring associated with that body. Upon downward movement of the retrieval means this other packing ring acts against the end of a tube which forms a portion of that body so as to rest in its plane and be in fluid-tight contact with a corresponding external tube so as to serve effectively as a piston. But upon reverse movement of the retrieval means under traction of the cable, the tube in question slides with respect to the rest of the means and is displaced from the packing ring which is no longer maintained toward the coring head and is deformed by the liquid which escapes past it.

Still further in known coring apparatus, there is danger of blockage of the parts that are supposed to move relative to each other.

In known coring operations, the water for cooling the apparatus and for flushing out drilling debris has to be introduced at relatively high pressure of the order of 140 to 170 pounds per square inch, so as to overcome the resistance to flexure of the sealing rings and thus to flow toward the coring bit. This high pressure of water requires a powerful pump and suitable water-tight conduitry. On the other hand, the packing rings which should effect the downward movement of the coring head and retrieval means toward their predetermined coring position are effective only at the beginning of their service because they are subjected on the one hand to mechanical erosion due to the passage of the water between the packing rings and the external tubes, at a speed of for example 3 or 4 feet per second, and on the other hand are subjected to cracking and deterioration by virtue of repeated flexure upon extraction of the cut cores. As a result, the packing rings must be frequently replaced, which immobilizes the entire equipment.

Accordingly, it is an object of the present invention to provide coring apparatus of the designated type, which may be operated at lower fluid pressure and whose parts are not subjected to destructive wear as in the known apparatus. It is also an object of the present invention to provide coring apparatus which will be relatively simple and inexpensive to manufacture, easy to operate, maintain and repair, and rugged and durable in use.

Briefly stated, the present invention overcomes these difficulties of the prior art and achieves the above objects, by employing a system in which the packing or sealing rings are not subjected to these deformations but remain in fluid-tight contact with their opposed surfaces at all times. In order to do this, the present invention provides passageways for the distribution of the fluid under pressure, adjacent but by-passing these sealing rings. In order to achieve this last result, in turn, the present invention provides relatively slidable parts which selectively open and close these passageways. As a result, it is possible to operate with lower pressure water, for example, about half the pressure previously used, or 70 to pounds per square inch.

Other features, objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is an elevational view of coring apparatus according to the present invention; 7

FIGS. 2a, 2b, 2c and 2d are axial cross sections, on an enlarged scale, of the structure shown in FIG. 1, these four figures being interconnectable with each other along the lines a-a, bb and c-c;

FIGS. 3, 4, 5, 6 and 7 are cross-sectional views taken respectively on the lines III-III, IV-IV, V-V, VI-VI and VII-VII of FIGS. 2a-2d;

FIGS. 8, 9, 10 and 11 are fragmentary cross-sectional views of the structure of FIGS. 2b, showing the operation of the coupling and uncoupling mechanism; and

FIGS. 12 and 13 are views of the structure shown in FIG. 2a, showing the operation of the retrieval mechanism.

In the various figures of the drawings, the same reference numerals refer to the same elements.

Referring now to the drawings in greater detail, there is shown coring apparatus of the cable type for drilling a core from the earth and recovering the core for purposes of examining specimens of the rock or soil at various depths. This coring apparatus comprises a chain of external tubes 1, 2, 3, 4 and 5 which are coaxial and which are rotatable about their common longitudinal axis by conventional drive means (not shown). The tubes are screw-threadedly interconnected.

The tube 1 carries an annular diamond coring bit 6 screwthreaded to its lower end (FIG. 2d). An annular guide ring 7 is fitted between the tubes 1 and 2, while an abutment stop ring 8 is secured between the tubes 2 and 3.

On its upper end, opposite the coring bit 6, the tube 3 has a thin-walled portion, shown in FIG. 2b, which with the adjacent end of tube 4 defines an annular coupling recess 9 whose purpose will be explained later.

The con'ng apparatus also comprises a coring head 10 (FIG. 20) generally known per se and having on the end thereof adjacent bit 6 an internal tube 1 l which is slidably guided by the annular guide ring 7. At its lower end, tube 11 carries an extractor 12 for the core which is cut from the earth by rotation and pressure of the coring bit 6. The extractor 12 permits extraction of the core which forms during drilling and which progressively enters the tube 1 1.

On its end opposite the coring bit 6, the coring head 10 comprises a string of coaxial interior tubes 13, 14 and 15. Tube 13 is screw-threadedly connected at its lower end to the principal portion of the head 10, while the tubes 13 and 14 are interconnected by an assembly pin 16 (FIG. 2b). Tubes 14 and 15 are mounted on an uncoupling member 17 which carries at least one coupling element 18 which releasably locks the coring head 10 in drilling position.

The uncoupling element 17 comprises on the one hand a forked portion 19 on the same side as coring bit 6 and has a longitudinal medial cleft 20; while on the other hand, the uncoupling element 17 has a tubular portion 21 disposed on the side opposite bit 6 and presenting a series of transversely aligned lateral openings 22 and an annular projection 23 extending toward the corresponding external tube 4. The forked portion 19 and the tubular portion 21 of the uncoupling element 17 are spaced apart axially by a divider 24 by which the uncoupling element is axially closed. It should be noted that the cross section of the lateral openings 22 is substantially equal to that of the annular space defined between the coring head 10 and the string of external tubes 1 to 5.

The coupling element 18 comprises at least one and preferably two latches 25 and 26 pivoted about an axle 27 whose ends are fixed in the internal tube 14. The latches 25 and 26 are thus disposed between the legs of the forked portion 19 of the uncoupling element 17, these legs defining between themselves the longitudinal cleft 20. The latches 25 and 26 are movable in opposite directions in the cleft 20.

A novel feature of the present invention is that the axle 27 carried by the internal tube 14 traverses two opposed elongated longitudinal slots 28 and 29 in the legs of the forked portion 19 of the uncoupling element 17. A tension spring 30 connects a pin 31 which is fixed to the internal tube 14, with a pin 32 which is secured to the lower end of the forked portion 19 of uncoupling element 17. Tension spring 30 urges the uncoupling element 17 and the internal tube 14 toward the coupled position.

Latches 25 and 26 are continuously urged outwardly by a spring 33 freely mounted in the cleft 20 and whose ends respectively engage the latches. However, at the beginning of withdrawal of the coring head from the external tubes 1 to 5, the latches 25 and 26 are forced inwardly, against the action of spring 33, under the influence of an uncoupling pin 34 fixed to the legs of the forked portion 19 of the uncoupling element 17 and extending diametrically between these legs. To this end, the uncoupling pin 34, whose ends are secured to those legs, is disposed continuously in two uncoupling slots 35 and 36 in the latches 25 and 26 (see FIG. 2b and FIGS. 3-11 The slots 35 and 36 are longitudinally elongated and in effect are comprised of two portions of which the lower has side walls parallel to the longitudinal axis of the apparatus and is relatively narrow, and the upper is of greater diameter and is generally inclined to that axis and has one marginal edge parallel to the longitudinal axis and the other marginal edge at an acute angle to the longitudinal axis. Preferably, the uncoupling pin 34 has two opposite planar surfaces that are parallel to the longitudinal axis of the apparatus. In drilling position, the uncoupling pin 34 engages in the lower portion of the slots 35 and 36 with its opposite planar side surfaces in contact with the edges of these lower slot portions. In this position (FIG. 2b), the uncoupling pin 34 altogether prevents pivotal movement of the latches 25 and 26 inwardly and maintains the outer portions of the latches in the annular coupling recess 9. In the illustrated embodiment, coupling abutment shoulder 37 is provided by the lower end of the tube 4 and is engageable with the upper outer corners of the latches 25 and 26 to limit upward movement of the latter.

Upon displacement of the coring head 10 from the drilling position, the uncoupling pin 34 will enter in the upper portions of the slots 35 and 36 and will then bear against the obliquely angled edges of these portions of the slots and will cam the latches inwardly against the action of spring 33. The latches 25 and 26 will thus be withdrawn from the recess 9.

The uncoupling element 17 is axially slidable in the tube 14 a distance equal to the length of the slots 28 and 29 or more precisely a distance equal to the distance between the centers of the semicircular ends of these slots. The sliding of the coupling element 17 in the tube 14 takes place shortly before or after the engagement of the coring head 10 with the abutment ring 8.

The internal tube 14 has a series of lateral openings 38 identical to the lateral openings 22 of the uncoupling element 17. The openings 38 are transversely aligned and are registrable with the openings 22. During sliding of the uncoupling element 17 in the tube 14, the lateral openings 38 may register with openings 22 or be out of registry therewith. The interior of the tubular portion 21 may thus communicate with the exterior of the tube 14 to a greater or lesser extent accordingly as these openings are or are not in registry with each other. The uncoupling element 17 and the tube 14 thus form together a slide valve for fluid distribution, as will be explained in greater detail hereinafter.

The tubular portion 21 of the uncoupling element 17 is connected to the internal tube by coaxial pins 39. An annular sealing ring 40 between spacer rings 41 encircles tubular portion 21 of uncoupling element 17, between the annular projection 23 and the adjacent end of tube 15. Sealing ring 40 serves as a pressure piston of the coring head 10 in the string of tubes 1 to 5 when moving toward coring bit 6.

The apparatus of the present invention also comprises retrieval means 42 for the coring head 10 with the core to be examined. These means are best seen in FIG. 2a, and comprise two catches 43 and 44 mounted for pivotal swinging movement about an axle 45 on a body 46 which has no axial passage therethrough. The lower ends of the catches 43 and 44 are continuously urged outwardly by a coil compression spring 47 disposed therebetween. Catches 43 and 44 thus engage releasably and with a snap action the upper end 48 of tube 15, under an upper marginal flange 49 thereon. In the position of the parts in FIG. 2a, therefore, the coring head 10 can be extracted and retrieved.

It is to be noted that the outward movement of the lower ends of catches 43 and 44 is limited by abutments 50 secured to body 46 and engageable with inclined edges 51 of the catches.

The body 46 of the retrieval means 42 also comprises an inner sleeve 52 and an outer sleeve 53. The inner sleeve 52 is mounted on body 46 by means of an assembly pin 54. The sleeve 53 is slidable along sleeve 52 and is urged downwardly relative to sleeve 52 by means of a coil compression spring 55.

The body 46 closes the lower end of sleeve 52, but the latter has a series of lateral openings 56 which may be opened or closed by sleeve 53. Thus, the sleeves 52 and 53, in various mutually slid positions, may or may not provide passageways for the admission of a fluid under pressure from the interior of sleeve 52 to the exterior of sleeve 53 (compare FIGS. 2a, 12 and 13). It should be noted that the area of the lateral openings 56 is about equal to that of the annular space between the retrieval means 42 and the string of tubes 1 to 5, which in turn is about equal to the area of the space between the coring head 10 and the string of tubes 1 to 5.

Sleeve 53 has an elastic deformable sealing ring 57 thereon between two spacer rings 58 that are disposed within a recess 59 in the lower end of sleeve 53. A snap ring 60 holds this assembly in position. Sealing ring 57 is continuously in contact with tube 5 and provides in effect a piston sliding in tube 5 and under the influence of fluid pressure urges the retrieval means 42 downwardly in the tubes 1 to 5.

Outer sleeve 53 also has a series of continuously open lateral openings 61 for the passage of fluid. Sleeve 53 is secured by assembly pins 62 to a connector 63 which has an axial opening to receive the lower end of a flexible cable 64 by which the entire internal slidable assembly may be raised.

In known fashion, the core is cut by bit 6 which rotates about its vertical axis and is driven downwardly along that axis. As the core forms, it progressively enters tube 1 1 through the extractor 12. Upon attaining a predetermined length, the core is detached from the bottom of the drilled hole and is brought to the surface. The coring head 10 and the retrieval means 42 are then reintroduced axially into the tubing 1 to 5, and the coring process is repeated.

The downward movement of the coring head 10 and the retrieval means 42 is efiected by fluid under pressure, for example water, until the lowermost position is attained which is permitted by the extent of the coring operation. Water under pressure thus presses against the tube 15 and the tubular portion 21 of the uncoupling element 17 and on the divider 24 and on the sealing ring 40 which forms an annular piston between the tube 15 and the external tubing 1 to 5. When the coring head 10 has reached the coring position, the uncoupling element 17 and the tube 14 are so disposed that the lateral openings 22 of the tubular portion 21 are closed by the end of tube 14 while the lateral openings 38 of tube 14 are closed by divider 24 (FIG. 8). Under these circumstances, water under pressure cannot pass through the openings 22 and 38 and accordingly exerts all its pressure on the coring head 10 to press it into coring position.

When the coring head has reached the downward limit of its movement, the tube 13 abuts against the abutment ring 8 (FIG. 2c). As a result, tube 14 remains stationary while the uncoupling element 17 continues to translate axially under the influence of the water under pressure. As a result, the uncoupling element 17 enters the tube 14 so that the uncoupling pin 34 engages in the lower portion of the slots 35 and 36 (FIG. 9). As a result, the latches 25 and 26 extend outwardly into the annular coupling chamber 9 so as to prevent return or upward movement of the coring head 10 by virtue of engagement with the annular abutment shoulder 37.

Depending on the extent of movement of uncoupling element 17 in the tube 14, the lateral openings 22 and 38 come progressively into registry with each other until the annular projection 23 of uncoupling element 17 is in contact with the adjacent end of tube 14 (FIG. 10). As soon as the openings 22 and 38 are in registry, water under pressure may pass therethrough, from the interior of tubular portion 21 to the exterior of tube 14, downwardly toward coring bit 6. At this time, the equalization of pressure retards the axial movement of uncoupling element 17 in tube 14 until it stops.

The coring head 10 is thus positioned for coring, and water under pressure which passes therethrough may then serve, during the coring operation proper, to cool the coring bit 6 and to flush up the coring debris between the tubes 1-5 and the wall of the drill hole.

After core formation, the coring head 10 is withdrawn from the tubes 1 to 5, by tension in the cable 64. At this time, tube and uncoupling element 17 slide first axially upwardly in distance corresponding to the length of the slots 28 and 29 as defined above, without causing any corresponding upward displacement of the tube 14 and the rest of the coring head 10. At this stage, the uncoupling pin 34 is disposed in the enlarged portion of the slots 35 and 36 and thus withdraws the latches 25 and 26 inwardly so as to disengage the latches from the coupling recess 9 thereby to uncouple the coring head. During the course of this separate sliding of the uncoupling element 17 in the tube 14 (FIG. 11), the lateral openings 22 and 38 are progressively closed, but immediately afterward they are gradually reopened so that the water may pass therethrough as freely as possible and pass thence to the interior of tubular portion 21 of uncoupling element 17 and to the exterior of the tube 14. It should be noted that in this latter position, the pin 27 is in the upper portion of slots 28 and 29 and thus ensures the return movement of the tube 14 and thus of the coring head 10, upon pulling on the uncoupling element 17 through the cable 64.

Of course the return or upward axial movement of the coring head 10 is possible only after the catches 43 and 44 engage under the flange 49 of the upper end 48 of tube 15.

The water under pressure acts against the connector 63, on the cross section of the sleeve 52, on the body 46 and on the sealing ring 57 which in turn acts as a piston between the sleeve 53 and the tubes 1-5.

Upon downward sliding of the retrieval means 42, the sleeve 53 abuts against the body 46 (FIG. 12), under the influence of the water under pressure. This continues until the retrieval means 42 reaches its lowermost position, and thus the retrieval means 42 is returned to its lowermost position by the pressure of the water.

Also, upon the extraction of the retrieval means 42 and the coring head 10 from the tubes 1-5, and at the beginning of this extraction (FIG. 13), the sleeve 53 slides first upwardly along the sleeve 52. This separate sliding of the sleeve 53 relative to the temporarily immobile sleeve 52 thus acts to compress the spring 55. After a certain amount of this separate sliding movement, lateral openings 56 of the sleeve 52 are progressively exposed by the sleeve 53 and permit the passage of water under pressure from the interior of sleeve 52 to the exterior of sleeve 53, whence the water passes downwardly. This escape of water results in a substantial reduction of the piston effect of retrieval means 42 and particularly that of the sealing ring 57 by reducing the piston effect to that of the transverse cross section of the connector 63.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved Although the present invention has been described and illustrated in connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

Having described my invention, I claim 1. In a cable-type coring apparatus comprising a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing, and means for retrieving the head with a cut core therein; the improvement in which said coring head comprises coaxial upper and lower tubes slidable relative to each other, said upper tube having lateral openings therethrough and an elastic deformable sealing ring encircling said upper tube above said lateral openings and in slidable sealing relationship with the interior of said string of tubing, said lower tube having lateral openings therethrough that move into and out of registry with said lateral openings through said upper tube upon sliding movement of said upper and lower tubes relative to each other, at least one latch pivotally mounted on said lower tube for swinging movement about a horizontal axis, said at least one latch being disposed between portions of said upper tube, said latch having a cam slot therein, and means on said portions of said upper tube engageable in said cam slot selectively to move said at least one latch about said horizontal axis upon relative movement between said inner and outer tubes.

2. In a cable-type coring apparatus comprising a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing and means for retrieving the head with a cut core therein, the improvement in which said coring head comprises:

a coaxial upper tube (21) having:

a transversely closed section (24) lateral openings (22) above said closed section (24) two elongated longitudinal slots (28, 29) diametrically opposed under the closed section (24) a diametral uncoupling pin (34) under said closed section and an annular projection (23) extending outwardly above the lateral openings (22),

an annular sealing ring (40):

carried by the upper tube (21) displaceable therewith and sealingly engaged within the tubing (4),

a coaxial lower tube (14), said upper and lower tubes (14, 21) being slidable relative to each other, said lower tube partially surrounding the upper tube (21) having lateral openings (38) located at its upper end and radially facing the lateral openings (22) of the upper tube (21) when the lower tube (14) abuts against the annular projection (23) of said upper tube (21 having two elongated longitudinal slots diametrically opposed perpendicular to the elongated slots (28, 29) of the upper tube (21) and located under the lateral openings (38) carrying an axle (27) extending through the elongated slots (28, 29) of the upper tube (21) two latches (25, 26)

pivotally mounted on the axle (27) of the lower tube l4) forced outwardly by a spring (33) engaged through the elongated slots of the lower tube engageable in a recess (9) of the tubing (3, 4) to be stationary therein having uncoupling slots (35, 36)

recess (9) of the tubing (3, 4), whereby the upper tube (21) moves farther downward within the stationary lower tube 14) under the influence of the spring (30) and the fluid pressure so that the lateral openings (3 8 and 22) of both upper and lower tubes (14, 21) face one another and fluid under pressure flows to the coring bit (6) and, during the upward movement of the head, the upper tube (21) drives upwardly the lower tube 14) whereby the latches are moved inwardly by the uncoupling pin 

1. In a cable-type coring apparatus comprising a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing, and means for retrieving the head with a cut core therein; the improvement in which said coring head comprises coaxial upper and lower tubes slidable relative to each other, said upper tube having lateral openings therethrough and an elastic deformable sealing ring encircling said upper tube above said lateral openings and in slidable sealing relationship with the interior of said string of tubing, said lower tube having lateral openings therethrough that move into and out of registry with said lateral openings through said upper tube upon sliding movement of said upper and lower tubes relative to each other, at least one latch pivotally mounted on said lower tube for swinginG movement about a horizontal axis, said at least one latch being disposed between portions of said upper tube, said latch having a cam slot therein, and means on said portions of said upper tube engageable in said cam slot selectively to move said at least one latch about said horizontal axis upon relative movement between said inner and outer tubes.
 2. In a cable-type coring apparatus comprising a string of tubing with an annular coring bit at its lower end, a coring head with a core extractor slidable within the tubing and means for retrieving the head with a cut core therein, the improvement in which said coring head comprises: a coaxial upper tube (21) having: a transversely closed section (24) lateral openings (22) above said closed section (24) two elongated longitudinal slots (28, 29) diametrically opposed under the closed section (24) a diametral uncoupling pin (34) under said closed section (24) and an annular projection (23) extending outwardly above the lateral openings (22), an annular sealing ring (40): carried by the upper tube (21) displaceable therewith and sealingly engaged within the tubing (4), a coaxial lower tube (14), said upper and lower tubes (14, 21) being slidable relative to each other, said lower tube (14) partially surrounding the upper tube (21) having lateral openings (38) located at its upper end and radially facing the lateral openings (22) of the upper tube (21) when the lower tube (14) abuts against the annular projection (23) of said upper tube (21) having two elongated longitudinal slots diametrically opposed perpendicular to the elongated slots (28, 29) of the upper tube (21) and located under the lateral openings (38) carrying an axle (27) extending through the elongated slots (28, 29) of the upper tube (21) two latches (25, 26) pivotally mounted on the axle (27) of the lower tube (14) forced outwardly by a spring (33) engaged through the elongated slots of the lower tube (14) engageable in a recess (9) of the tubing (3, 4) to be stationary therein having uncoupling slots (35, 36) partly facing each other and transversed by the uncoupling pin (34) of the upper tube (21) a spring (30) connecting both upper and lower tubes (14, 21) and resiliently forcing them to slide towards each other, so that: during the downward movement of the head under the action of fluid pressure, the upper tube (21) with its closed section( (24) and its sealing ring (40) with its lateral openings (22) obturated by the lower tube (14) acts as a piston until the latches (25, 26) engage in the coupling recess (9) of the tubing (3, 4), whereby the upper tube (21) moves farther downward within the stationary lower tube (14) under the influence of the spring (30) and the fluid pressure so that the lateral openings (38 and 22) of both upper and lower tubes (14, 21) face one another and fluid under pressure flows to the coring bit (6) and, during the upward movement of the head, the upper tube (21) drives upwardly the lower tube (14) whereby the latches are moved inwardly by the uncoupling pin (34). 